Pressure releasing device



March 31 1953 K. B. BREDTSCHNEIDER 2,633,151

PRESSURE RELEASING vmamar:

4 Sheets-Sheet 1 Filed April 25, 1951 Fig. 6

3o 28 k j /1 3' 6, 5| 42 45 O 44 32 54 lo o 4%, 2o l? sa 3 mvENToR ATTORNEY March 31, 1953 K. B. BREDTscHNElDER 2,633,151

PRESSURE RELEASING DEVICE Filed April 25, `1951 4 Sheets-Sheet 2 elder INVENTOR Bredsc l n ATTORNEY Kuri l l l l 1 1 1 l l l l l l 1 l l 1 l l l 1 l l l 1 l n 1 Mardi 31, 1953 K. B. BREDTscHNElDER 2,633,151

PRESSURE RELEASING DEVICE Filed April 25, 1951 4 Sheets-Sheet 3 INVENTOR AToRNEY March 31 1953 K. B. BREDTscHNElDl-:R 2,633,151

PRESSURE RELEASING DEVICE Filed April 25, 1951 `4 Sheets-Sheet 4 bl Fig. /3

b n f P' m n: D 4 m m u.: n: 9 n.

P2 Fig. l2

1 f PI Expanson e p2 Compression PISTON STROKE Fig.

INVENTOR- Kurt BLBredtschn i er E swf TORNEY valve.

Patented Mar. 31, 1953 PRESSURE RELEASING DEVICE Kurt B. Bredtschneider, Chicago, Ill., assigner to the United States of America as represented by the Secretary of the Interior Application April 25, 1951, Serial No. 223,692

9 Claims.

The invention herein described and claimed may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of royalties thereon or therefor.

This invention is concerned with a device for releasing a uid from a zone of relatively high pressure to a Zone of lrelatively low pressure which is particularly suitable for releasing the pressure from fluids having erosive properties.

The problem of discharging a fluid from a zone of high pressure to a low pressure zone presents considerable diiiiculties when the fluid is of an erosive character, for example, where the fluid involved is a solids-in-gas suspension, or a solids-in-liquid suspension, or a solids-inliquid suspension also containing dissolved gases. Because of the high pressure differentials involved, the erosive uid tends to flow at extremely high velocities through the valves of ordinary pressure releasing mechanisms, thereby quickly ruining the valve surfaces. A number of devices have been previously suggested for releasing the pressure from erosive fluids which are constructed so as to avoid these abnormally high velocities of flow through the releasing valve, thereby avoiding the rapid deterioration of thel valve. One such device is described in U. S. Patent No. 2,012,319 issued to Hermann Pittlick on August 27, 1935, and entitled Pressure Releasing Device. Thisdevice includes a cylinder,

l having a piston mounted for reciprocation therein, which serves as an intermediate chamber between the high pressure and low pressure zone for decompressing the high pressure liuidbefore it `is discharged through the outlet valve to the low pressure zone. In order to avoid excessive velocities through the inlet valve which communicates with the high pressure zone, the inlet and outlet valves are opened and closed in timed relation with the reciprocations ofthe piston such that a portion of the decompressed fluid is retained in the cylinder, and recompressed to a pressure approximating that in the high pressure Zone, before the inlet valver is opened to admit additional high pressureuid to the cylinder.

Under normal conditions this device operates quite satisfactorily. However, if normal operations are disturbed, for example, by leakage of the inlet or outlet valves, or by a sudden change in the composition of the high pressure fluid, it sometimes happens that the desired pressure equalization across the inlet or outlet vvalve does not occur prior to the opening of the Since in this prior device, the'inlet and.

. ditions; and,

, 2 outlet valves are opened in a predetermined rhythm, irrespective of the pressure differential existing across the valve, under abnormal conditions of operation this prior device fails to prevent excessive velocities through the valves, and in some cases Aeven permits the free access ofthe high pressure fluid through the cylinder to the low pressure zone.

The object of the present invention is to provide a pressure releasing device similar to the device described in the above identified patent, but free from the disadvantages connected with this prior device. More specically, the object of the invention is to improve the safety of this prior device by assuring that when pressure equalization across the valves fails to take place because of some abnormal condition of operation, the valves will fail to open, and the device will come to a stop of itself.

These objects are accomplished in accordance with the present invention, by providing means for opening the inlet and outlet valves which exert controlled predetermined forces against these valves such that the valves are opened only when a predetermined permissible pressure differential exists across the valve. Thus, the opening of the valves does not depend upon any predetermined established rhythm but depends only upon the existence of a permissible pressure differential across the valve. The valve closing means, on the other hand, act against the forces tending to open the inlet and outlet valves, and

'cause these valves Vto close in a predetermined rhythm timed in accordance with the reciprocations of the piston.

For a fuller description and better understanding of the invention, reference is now made to the accompanying drawings wherein:

Fig. 1 is an illustration of one embodiment of the invention; and,

Figs. 2 to 5, inclusive, illustrate the operation of the embodiment shown in Fig. 1 at various stages in its operating cycle; and,

Fig. 6 is an illustration of a second embodiment of the invention; and,

Figs. 7 to 10, inclusive, illustrate the operation of the embodiment shown in Fig. 6 at various stages in its operating cycle;` and,

Fig. 11 is a diagram showing the operating cycle ofa device constructed in accordance with the invention when operating under normal con- Fig. 12 is a diagram showing the operation of a device constructed accordancewith the invention when the inletvalve` is leaking; and,

Fig. 13 is a diagram showing the operation of 3 a device according to the invention when the outlet valve is leaking.

Referring now particularly to Fig. l, reference numeral I refers to a high pressure vessel containing a fluid under high pressure and connected by line 3 to the inlet side of the pressure releasing device of the invention. Numeral 2 refers to a low pressure vessel for storing decompressed fluid and connected to the outlet side of the pressure releasing device by line 4. The pressure releasing device itself comprises a cylinder 5 equipped with a piston 6 mounted for reciprocation in the cylinder for producing alternating compression and expansion strokes. The piston 5 is connected by a piston rod 1,` a connecting rod 8, a crank shaft 9, to a flywheel I (see Fig. 6).

An inlet valve I I, arranged in valve chamber I2 provides communication between the high pressure vessel I and the interior of the cylinder 5. Movement of the valve II is controlled by valve rod I3 which is mounted in a journal supported by valve casing I4. A spring I5, held in compression between valvecasing I4 and a nut I3a on the lower end of the valve stem I3, exerts a predetermined force tending to force the valve II to the open position. A cam I6 operates a bell crank I'I pivoted at I8, one end of which follows the contour of cam I6, and the other end of which operates against the valve stem I3. This cam and bell crank system alternately closes the valve II against the opposing force of spring I5, and releases it at timed intervals during the operation of the device.

An outlet valve I9 at the top of the cylinder provides communication between the low pressure vessel 2 and the interior of the cylinder. Valve I9 is operated by a valve stem. 2| journaled in valve casing 29. A spring 22, held in compression between shoulder 23 provided on the valve stem 2l and packing nut 24, exerts a predetermined force against the valve stem tending to force the valve I9 to the open position. A suitably contoured cam 25 operates a bell crank 25, pivoted at 21, for alternately closing the valve I9 against the force of spring 22 and releasing it at timed intervals during the operation of the device.

The amount of force exerted by springs I5 and 22 for biasing valves I I and I9 respectively to the open position is adjusted so that these valves will only open when the pressure differential on opposite sides thereof is within predetermined permissible limits. In this way, if the differential pressure between the valve chamber I2 and the interior of the cylinder or the differential pressure between valve chamber I9a and the interior of the cylinder is excessive, such that an undesirably high velocity of flow through either of the valves would occur, the valves will remain closed. The maximum permissible differential pressure across either of the valves which will not result in erosive damage to the valve surfaces, of course, will depend upon the properties of the particular liquid being handled, and consequently the amount of opening force which the springs are permitted to exert will be governed accordingly.

The cams I6 and 25 rotate at the proper speed in accordance with the reciprocations of the piston 5 to insure the actuation of the valves I I and I9 respectively at the proper intervals during the operating cycle. Preferably the rotation of the cams is controlled directly by the piston 5, each of the cams being connected to the piston through `suitable mechanism to insure a constant relationship between the reciprocations of the piston and the operation of the cams.

To provide for adjustment of the operating cycle to accommodate iuids of varying composition the cam contour is preferably constructed so as to be capable of adjustment in a manner, for example, as is shown in the drawings. As will be apparent from the subsequently description, the timing of the inlet valve particularly depends upon the compressibility of the fluid being decompressed.

Reference is now made to Figs. l to 5, inclusive, which illustrates the embodiment shown in Fig. 1 in the various stages of its operating cycle. The reciprocation of the piston 6 in the cylinder produces alternate expansion strokes, when the piston moves to the left as viewed in the drawing, and compressionstrokes, as the piston moves to the right.

One complete cycle of the device includes an expansion and a compression stroke. During the rst part of the expansion stroke, the inlet valve il is open and high pressure fluid iiows into the cylinder. Before the completion of the expansion stroke, the inlet valve I I is closed permitting the iiuid in the cylinder to undergo decompression. Before the beginning of the compression stroke, the outlet valve opens, thus permitting the decompressed fluid in the cylinder to be discharged through the outlet valve I9 to the low pressure vessel 2. Before the end of the compression stroke, the outlet valve I9 is closed thus permitting residual fluid trapped in the cylinder to be recompressed to a pressure approximating that in the high pressure vessel l. Near the end of the compression stroke, the inlet valve I I opens again allowing excess fluid, if any, to be pushed back into the high pressure vessel. The inlet valve remains open when the device begins another cycle as the piston begins another expansion stroke, permitting an additional charge of high pressure fluid to be introduced into the cylinder.

In the embodiment shown power for reciprocating the piston 5 is furnished by the energy released during decompression of the high pressure uid. Flywheel i0 stores sufficient energy to produce recompression of Dart of the decompressed fluid at the end of the compression stroke. Residual energy, if any, produced by the device can be utilized in any desired manner.

Fig. l shows the device at the beginning of the expansion stroke as high pressure fluid from vessel is introduced into the cylinder. The valve II is held open by spring I5, the cam I6 being in a position such that no closing force is exerted upon the valve II. The piston 6 is moving to the left, allowing high pressure fluid to flow into the cylinder. Cam 25 has moved to a position such that valve I9 is positively held in the closed position.

Fig. 2 shows the device in a later part of the expansion stroke, with the piston 6 still moving to the left. The introduction of high pressure iluid into the cylinder has ceased, and decompression of the uid in the cylinder has begun. The cam I6 has now moved to a position such that, through the action of bell crank I'I acting against the spring l5, valve II is closed. Outlet valve I9 is still held in a closed position by cam 25 and bell crank 26.

Fig. 3 shows the device at the end of the expansion stroke. The fluid in the cylinder has now been decompressed to a pressure approximating that in the low pressure vessel. The cam 25 has moved to a position such as to release the bell crank 26, permitting the valve I9 to be opened by the action of spring 22, provided the pressure s 'differential' between the valve chamber l9a and the interior of thecylinder is within permissible limits. In normal operation suflicient decompression will take place during the expansion stroke so that this will be the case, and valve I9 will open near the end of the expansion stroke as shown. rIhe inlet valve l I is held closed at this point by the differential pressure between the interior of the cylinder and valve chamber l2 which is greater than the opening force of spring l5. If desired, the inlet valve Il at this point may be also held closed by the positive action of cam I6 and bell crank l1.

Fig. 4 shows the device during the rst part of the compression stroke, with the piston 6 moving to the right causing decompressed fluid to be `discharged through valve chamber l9a to the low pressure vessel. Cam 25 is still in a position such as to permit spring 22 to hold valve I9` in the open position. Inlet valve II is held in a closed position by the differential pressure between the interior of cylinder 5 and valve chamber I2 which is greater than the opening force of spring l5.

Fig. shows the device toward the end of the compression stroke, with the piston E still moving towards the right. Cam 25 has moved to a position such as to cause the bell crank 26 to close valve I9 against the opening force of spring 22. This has occurred before all of the decompressed fluid has been discharged into vessel l, thereby trapping residual uid in the cylinder. As the piston 6 continues to move towards the right this residual fluid is recompressed until its pressure becomes approximately that of the fluid in the high pressure zone. When the pressure differential between the fluid in the cylinder and that in valve chamber I2 comes within predetermined permissible limits, the opening force exerted by spring l5 is sufcient to open the valve lfl, cam I6 being in such -a position as to permit this to occur. As shown in Fig. 5, valve ll has just opened, and a small amount of residual fluid is being pushed back into the high pressure vessel I. If for any reason (such as a leaky outlet valve) reoompression of the fluid trapped in the cylinder should not occur, or only occur to a limited extent, such that the pressure differential between the fluid in the cylinder and the fluid in valve chamber l2 is excessive, the force exerted by spring l5 would not be sufficient to overcome this pressure differential and the valve ll would not open.

Reference is now made to Fig. 11 wherein piston strokes are plotted against pressure in the cylinder during a normal operating cycle. The pressure pl corresponds to the pressure existing in the high pressure vessel and the pressure p2 corresponds to the pressure in the low pressure vessel. As the piston begins its expansion stroke at a, the pressure in the cylinder is equal to pl. From a, to b, as high pressure fluid is introduced into the cylinder through the inlet valve I l, the pressure in the cylinder remains equal to pl. At b, the inlet` valve ll is closed, decompression of the fluid in the cylinder begins, and pressure in the cylinder becomes smaller. From b to d decompression of the fluid in the cylinder continues reached where the differential pressure is not excessive. in the cylinder is discharged into the low pressure From d to e, the decompressed fluid -the pressure in the cylinder equals p2.

vessel '2. `At e, the outlet valve lI9 is closed.

From c to f the residual fluid trapped in the cylinder is recompressed to a pressure approximately equal to pl. At point f, when the differential pressure between the cylinder and valve -in a closed position. pl is equal to the pressure lin the high pressure vessel and p2 is the pressure in the low pressure vessel. At point a, the piston begins its expansion stroke. The inlet valve Il is open, and the pressure in thecylinder is equal to pl. At bi, valve ll is closed but high pressure fluid leaks past the valve. From b'to y the material in the cylinder is decompressed, but pressure p2 is not attained since more high pressure fluid has leaked into the vessel past valve Il. Since the pressure in the cylinder at point g is greater than the permissible differential pressure between the fluid in the cylinder and valve chamber l9a, spring 22 would not exert suiiicient force to open the outlet valve and consequently the outlet valve I9 will remain closed. In this situation, in the case of the prior device described in the above identified U. S. patent, the outlet valve would have been opened regardless of the high pressure differential existing across the valve, thus permitting high pressure fluid in the cylinder to now into the low pressure vessel with consequent damage to the valve surfaces, and perhaps damage or destruction of the low pressure lines. According to the invention however, the outlet valve I9 does not open, there is no discharge into the low pressure vessel. From g to f, the iiuid in the cylinder `will be recompressed to its original pressure pl.

Inlet valve Il will then be opened by spring l5 and the material in the cylinder will be pushed back into the high pressure vessel. Since all the uid which is decompressed to pressure g is recompressed to its original pressure, there is no net decompression and consequently no release of energy. Consequently, the device will slow down and eventually stop of itself when the energy stored in the flywheel I9 is used up.

Reference is now made to Fig. 13 which shows the operation ofthe device in the event that the outlet valve I9 becomes damaged, permitting fluid to leak past it when in a closed position. At point d, at the beginning of the compression stroke, the outlet valve I9 is open, and From d to e, decompressed fluid is discharged into the low pressure vessel. At point e the outlet valve I9 is closed but fluid leaks past the valve. From e to h, compression of the uid trapped in the cylinder to a pressure hn is obtained. Recompression to pressure pl is not obtained because of the leaky valve I9. Since the presure differential between the uid in the cylinder and the high pressure fluid in valve chamber l2 is greater than the permissible pressure differential, spring l5 will-not open valve ll. In this same situation, in the case of the prior device referred to above, the valve ll would have been opened re gardless of the pressure differential existing across it, thus permitting high pressure fluid to flow directly into the low pressure vessel l throughthe leaky valve I9. With the deviceof the invention, however, the inlet valve does not open and consequently high pressure fluid from vessel does not enter the cylinder. vFrom hto e, as the piston begins its .expansion stroke, the residuallluid inthe cylinder is decompressed back to the pressure p2. From e to bl, depending upon the 'extent of leakage in the outlet vvalve I9, the pressure in the cylinder drops more or less below p2. At bl the closing force on the outlet valve IS is released bythe cam 25, and valve I9 is opened by spring 22. As the piston completes the expansion strokefrom bl to d, the pressure .in the cylinder becomes equal to p2. As iin the previous case, there is 'no net decompression of the fluid, and consequently no energy released, and therefore, as :inthe previous case, the device will stop .of itself when rthe energy of the flywheel lli is used up.

Under other abnormal conditions of operation which result in the failure of the desired pressure equalization vto take place across the inlet or routlet valve at the moment itis scheduled Vto open, the device will operate in a similar way to prevent vthe valve from opening. For example, if for some reason there is a change in the composition of the fluid being released, such, for example, as an increase inthe pressure of a gas being released, the outlet valve will fail to open if the 'expansion stroke .is too short to sufficiently `decompress the gas. Similarly, if, when releasing a fluid consisting of a liquid containing dissolved gases under high pressure, for some reason there is an increase in the amount of gas that is dissolved in the liquid, the outlet valve will likewise fail to open if the expansion stroke is too short to suiciently decompress the mixture of gas .and liquid.

Any suitable means, other than springs as shown in the embodiment illustrated in Figs. 1 -to 5 may be employed for exerting predetermined forces on the inlet and outlet valves tending to bias them to the open position. For example, instead of springs, weights, attached to valve .stems 2| and I3, respectively, may be employed to exert these predetermined forces.

A still different arrangement is shown in Figs. 6 to 10, inclusive, where the predetermined forces for opening the inlet and outlet valves lare supplied by pistons operated by fluidfrom the high pressure and low pressure zones, respectively.

Referring now particularly to Fig. 6, reference numeral 28 refers to a high pressure vessel connected by line 2.9 to the intake side of the pressure releasing device. A low pressure vessel .30 is connected by line 3i to the outlet side of the device. As in the `previously describedembodiment, the vpressure releasing device comprises a cylinder 33 .having a piston 32 mounted for reciprocation therein. The piston 32 connected to a .flywheel in the same manner as in the previously described embodiment. The inlet device is of the ball check type, including a ball v34 and a spring 35 for forcing the ball against the valveseat. The outlet Avalve is likewise of the ball check type, including ball 36 biased against the valve seat'by .spring 3l. If desired, any other convenient type of check valve may be used, such -as a disk check valve in vplace of the ball check valves shown. A passage 38 provides communication between the outlet and inlet valves, and between the inlet valve and the interior of .the cylinder.

Above the inlet valve, a cylinder 3.9- is provided, connected by line 45 to .the high pressure vessel 23. A piston 4|, suitably packed, slides in the cylinder 39. At .its lower end, the piston 4| .is

`fastened `to a crankslide 42. Crankslide .42 is in turn fastened to a push rod 43 which extends through a suitablegland 44, and is positioned so as to depress the ball-34 'when the piston 4| moves downwardly. A suitably contoured cam 45 operates a bell crank 46 the opposite end of which operates in crankslide 42. The cross-sectional area roi piston 4|, of the .rod 43, and the ball 34, land the size of `the inlet valve opening, are so proportioned in relation to one another that the piston-4 l, which is actuated by fluid pressure from the high pressure vessel 28, will exert a force against the ball check valve 34 sulicient to open it only when a predetermined permissible pressure differential exists across the valve. It is clear o'f course that the piston 4| must exert at least enough force to overcome stuffing box friction and the force exerted by spring 35.

The cam 45 is properly contoured and rotates at the proper rate in timed relation with the reciprocations of the piston 32, such that at proper intervals during the operation of the device, the piston 4| is pushed upwardly against the V:force of the high pressure iluid exerted against it, thus permitting the inlet valve to be closed by the action of spring 35. Likewise, at the proper intervals, the cam 45 releases the piston 4| allowing it to open the inlet Valve 34 if the pressure differential is not excessive.

Above the outlet valve, a second cylinder 4l is provided, connected to low pressure vessel 3G by line 43, and having a piston 49 mounted for reciprccation therein. Fastened to the lower end of piston 49 is a crankslide 5D and push rod 5|. The push rod -acts in a similar manner to the push rod 43 to open the outlet valve by depressing ball 35 against the opposing force of spring 3l. The piston 49, push rod 5|, ball 36, and the size of the outlet valve opening, are so proportioned that push rod 5| will exert a force such as to open the outlet valve only when the pressure differential across the valve is within predetermined permissible limits.

A cam 52 operates a bell crank 53, one end 'of which follows the cam contour, and the other end of which operates in crankslide 59. The cam 52 is properly contoured, and rotates at the proper rate in timed relation with the reciprocations of the piston 32,

Vcomprises an expansion and compression stroke.

Fig. 6 shows the device shortly after the beginvning of the expansion stroke the inlet valve 34 fbeing open, and the outlet valve 35 being closed.

High pressure fluid from vessel 28 flows into the cylinder through the linlet valve.

Fig. `7 shows the device during a later part of the expansion stroke, the piston Yi2 still moving to the left. The cam 45 has pushed the piston 4| upwardly against the'iluid pressure in cylinder 39, thereby releasing the ball 34 allowing spring 35 to close the inlet valve. Cam 52 holds push rod 5| away from the outlet valve. At this point, decompression of the fluid in the cylinder begins.

Fig. `8 vshows the device near the completion Y 9 of its expansion stroke, the piston 32 still moving towards the left. The inlet valve is still closed,

but cam 52 has released the piston 49 allowing` push rod 5l to open the outlet valve by depressing the ball 36.

Fig. 9 shows the device in the rst part of its compression stroke, with the piston 32 moving f towards the right, discharging decompressed fluid through the open outlet valve into the vessel 30.

Fig. l shows the device towards the end of its compression stroke with the piston 32 still moving towards the right. Shortly before, cam 52 has raised push rod I, thus permitting the spring 31 to close the outlet valve. The residual liquid' It is apparent of course, that if normal operation should be disturbed, and for some reason equalization across either the inlet or outlet valve fails to take place at the moment when either of these valves would ordinarily open, these valves will fail to open and the device Will automatically come to a stop as in the previously described embodiment.

i As previously stated, the device of the invention is particularly suitable for releasing pressure from fluids having erosive properties. For example, the device of the invention will be found particularly useful in plants for the conversion of coal into hydrocarbons by high pressure hydrogenation according to the so-called Bergius process; In this process, the coal, carried in a heavy oil vehicle is subjected to treatment with hydrogen at pressures in the order of 10,000 to 20,000 pounds per square inch. In the course of this process, a heavy asphaltic oil is formed which is collected in a vessel called the hot catchpot Where it is stored temporarily under an atmosphere of hydrogen at a pressure of 10,000 to 20,000 pounds per square inch. This heavy oil containing dissolved hydrogen, also contains the ash content of the coal and catalyst particles suspended therein. Due to the high pressures involved and the erosive character of this heavy oil, it is quite difficult to let down to atmospheric pressure.

Using the device of the invention however, this 'can be accomplished safely and with little Wear and tear on the pressure releasemechanism Furthermore, in a large plant, usable amount of energy released by decompression of the heavy oil may be recovered.

When releasing a liquid containing dissolved gasunder high pressurey the amount of decompression necessary to reach a specied lower pressure Will depend chiefly upon the amount of gas dissolved in the liquid. In utilizing the device of the invention for releasing a mixture of this type, the amount yof decompression can readily be adjusted by altering the contour of the cam controlling the inlet valve so as to close the inlet valve at the proper time during the expansion stroke. The sooner the inlet valve is closed during the expansion stroke, the greater amount of decompression will take place, and conversely.

When releasing a liquid containing dissolved gases under high pressure, it is preferable that at least the outlet valve be located at the top of the cylinder as in the two embodiments described above. In this way, if any residual pressure difl0 ferential within the permissible limits exists with-'- in the cylinder, the gas which collects at the top ofthe cylinder may vent itself first at a relatively high velocity, releasing this residual pressure without causing wear on the valve. The erosive liquid which collects at the bottom of the cylinv der is then pushed out by the piston at a relatively low velocity.

It is to be understood that the' above description, together with the specific examples and embodiments described, is intended merely to illustrate the invention, and that the invention is not to be limited thereto, nor in any way except by v' the scope of the appended claims,

I claim: 1. A device for releasing a fluid from a zone of relativelyhigh pressure to a zone of relatively low k pressure comprising a cylinder, a piston mounted for reciprocation in said cylinder for producing alternating expansion and compression strokes,V an inlet. valve for admitting a fluid under relatively high pressure into said cylinder, anoutlet Y valve for releasing said fluid in a decompressed` low pressure comprising a cylinder, a piston. mounted for reciprocation in said cylinder for.

producing alternating expansion and compression strokes, an inlet valve for admitting a fluid under relatively high pressure into said cylinder, an outlet valve for releasing said fluid in a decompressed condition from said cylinder to a zone of relatively low pressure, means exerting predetermined forces against said inlet and outlet valves for causing said valves to open onlywhen the pressure differential across said valves is within predetermined permissible limits, means' acting against the force tending to open said inlet valve for causing said inlet valve to close prior to the completion of each expansion stroke, means acting against the force tending to open said outlet valve for causing said outlet to close prior to the completion of each compression stroke.

3. A device for releasing a fluid from a zonev of relatively high pressure to a zone of relatively low pressure comprising va cylinder, a piston mounted for reciprocation in said cylinder for producing alternating expansion and compression strokes, arr inlet valvefor admitting uid under relatively high pressure into said cylinder, an outlet valve for releasing said uid in a decompressed condition` from said cylinder to av zone of relatively low pressure, means exerting predetermined forces againstsaid inlet and outlet valves for causing said valves to open only when the pressure differential across said valves is within predetermined permissible limits, means acting against the force tending to open said inlet valve for causing said inlet valve -to close prior to the completion of each expansion stroke, means for releasing said inlet valve closing means prior to the completion of each compression stroke, means acting against the force tending to open said outlet valve for causing said outlet -valve to close prior to the completion of-each' compression stroke, and means for releasing said outlet valve closing means prior to the completion of each expansion stroke.

4. A device for releasing a fluid from a zone of relatively high pressure to a zone of relatively low pressure comprising a cylinder, a piston mounted for reciprocation in said cylinder for producing alternating expansion and compression strokes, an inlet valve for admitting a uid under relatively high pressure into said cylinder, an outlet valve for releasing said fluid in a decompressed condition from said cylinder to a Zone of relatively low pressure, means exerting predetermined forces against said inlet and outlet valves for causing said valves to open only when the pressure differential across said valves is Within predetermined permissible limits, means acting against the force tending to open said inlet valve for causing said inlet valve to close prior to the completion of each expansion stroke, means for releasing said inlet valve closing means prior to the completion of each compression stroke, means acting against the force tending to open said outlet valve for causing said outlet valve to close prior to the completion of each compression stroke, means for releasing said outlet valve closing means prior to the completion of each expansion stroke, said means for closing and releasing said inlet and outlet valves including cams operated in timed relation with the reciprocations of said piston.

5. A device for releasing a fluid from a zone of relatively high pressure to a zone of relatively loW pressure comprising a cylinder, a piston mounted for reciprocation in said cylinder for producing alternating expansion and compression strokes, an inlet valve for admitting a iiuid underrelatively high pressure into said cylinder, an outlet valve for releasing said fluid in a decompressed condition from said cylinder to a zone of relatively lovv pressure, means exerting a predetermined force against said inlet valve for opening said valve prior to the beginning of each expansion stroke, said opening force being adjusted so as to cause said inlet valve4 to open only when the pressure differential across said inlet valve is Within predetermined permissible limits, means acting against the force tending to open said inlet valve for causing said inlet valve to close prior to the completion of each expansion stroke, means exerting a predetermined force against said outlet valve for opening said Valve prior to the beginning of each compression stroke, said opening force being adjusted so as to cause said outlet valve to open only when the pressure diierential across said outlet Valve is Within predetermined permissible limits, means acting against the force tending to open said outlet valve for causing said outlet valve to close prior to the completion of each compression stroke.

6. A device for releasing a fluid from a zone of relatively high pressure to a zone of relatively low pressure comprising a cylinder, a piston mounted for reciprocation in said cylinder for producing alternating expansion and compression strokes, an inlet valve for admitting a uid under relatively high pressure into said cylinder, an outlet valve for releasing said fluid in a decompressed condition from said cylinder to a zone of relatively low pressure, means exerting a predetermined force against said inlet valve for opening said valve prior to the beginning of each expansion stroke, said opening force being adjusted so as to cause said inlet valve to open only when the pressure differential across said inlet valve is Within predetermined permissible limits, means acting against the force tending to open said inlet valve for causing said inlet valve to close prior to the completion of each expansion stroke, means for releasing said inlet valve closing means prior to the completion of each compression stroke, meansv exerting a predetermined force against said outlet valve for opening said valve prior to the beginning of each compression stroke, said opening force being adjusted so as to cause said outlet valve to open only when the pressure diierential across said outlet valve is within predetermined permissible limits, means acting against the force tending to open said outlet valve to cause said outlet valve to close prior to the completion of each compression stroke, and means for releasing said outlet valve closing means prior to the completion of each expansion stroke.

7. A device for releasing a uid from a zone of relatively high pressure to a zone of relatively low pressure comprising a cylinder, a piston mounted for reciprocation in said cylinder for producing alternating expansion and compression strokes, an inlet Valve for admitting a fluid under relatively high pressure into said cylinder, an outlet valve for releasing said fluid in a decompressed condition from said cylinder to a zone of relatively low pressure, means exerting a predetermined force against said inlet valve for opening said valve prior to the beginning of each expansion stroke so as to permit uid from said high pressure zone to be introduced into said cylinder, said. opening, force being adjusted so as to cause said inlet valve to open only when the pressure differential across said inlet valve iswithin predetermined permissible limits, means acting against the force tending to open said inlet valve for causing said inlet valve to close prior to the completion of each expansion stroke so as to permit said fluid to undergo decompression in said cylinder, means exerting a predetermined force against said outlet valve for opening said valve prior to the beginning of each compression stroke so as to permit the discharge of said decompressed uid to said low pressure zone, said opening force being adjusted so as to cause said outlet valve to open only When the pressure differential across said outlet Valve is Within predetermined permissible limits, means acting against the force tending to open said outlet Valve for causing said outlet valve to close after the bulk of said decompressed fluid has been discharged into said low pressure Zone but prior to the completion of the compression stroke so as to permit residual'luid in said cylinder to be recompressed to a pressure approximating the pressure in said high pressure zone.

8. A device for releasing a uid from a zone of relatively high pressure to a zone of relatively low pressure comprising a cylinder, a piston mounted for reciprocation in said cylinder for producing alternating expansion and compression strokes, an inlet valve for admitting a fluid under relatively high pressure into said cylinder, an outlet valve for releasing said duid in a decompressed condition from said cylinder to a zone of relatively low pressure, means exerting a predetermined force against said inlet valve for opening said valve prior to the beginning of each expansion stroke so as to permit fluid from said high pressure zone to be introduced into said cylinder, said opening force being adjusted so as to cause said inlet valve to open only when the pressure differential across said inlet valve is within predetermined permissible limits, means acting against the force tending to open said inlet valve for causing said inlet valve to close prior to the completion of each expansion stroke so as to permit said fluid to undergo decompression in said cylinder, means exerting a predetermined force against said outlet valve for opening said valve prior to the beginning of each compression stroke so as to permit the discharge of said decompressed fluid to said low pressure zone, said opening force being adjusted so as to cause said outlet valve to open only when the pressure differential across said outlet valve is within predetermined permissible limits, means acting against the force tending to open said outlet valve for causing said outlet valve to close after the bulk of said decompressed iiuid has been discharged into said low pressure zone, but prior to the completion of the compression stroke, so as to permit the residual uid in said cylinder to be recompressed to a pressure approximating the pressure in said high pressure zone, means for releasing said inlet valve closing means prior to the completion of each compression stroke, and means for releasing said outlet valve closing means prior to the completion of each expansion stroke.

9. A device for releasing a fluid from a zone of relatively high pressure to a zone of relatively low pressure comprising a cylinder, a piston mounted for reciprocation in said cylinder for producing alternating expansion and compression strokes, an inlet valve for admitting a fluid under relatively high pressure into said cylinder, an outlet valve for releasing said iiuid in a decompressed condition from said cylinder to a zone of relatively low pressure, means including a piston actuated by high pressure fluid from said high pressure zone for exerting a predetermined force against said inlet valve for opening s-aid valve prior to the beginning of each expansion stroke so as to permit uid from said high pressure zone to be introduced into said cylinder, said opening force being adjusted so as to cause said inlet valve to open only when the pressure differential across said inlet valve is within predetermined permissible limits, means acting 'against the force tending to open said inlet valve for causing said inlet valve to close prior to the completion of each expansion stroke so as to permit said iiuid to undergo expansion in said cylinder, means including a piston actuated by decompressed fluid from said low pressure zone for exerting a predetermined force against said outlet valve for opening said valve prior to the beginning of each compression stroke so as to permit the discharge of said decompressed fluid to said 10W pressure zone, said opening force being adjusted so as to cause said outlet valve to open only when the pressure differential across said outlet valve is within predetermined permissible limits, means acting against the force tending to open said outlet valve for causing said outlet valve to close after the bulk of said decompressed uid has been discharged into said low pressure zone but prior to the completion of the compression stroke so as to permit the residual fiuid in said cylinder to be recompressed to a pressure approximating the pressure in said high pressure zone.

KURT B. BREDTSCHN'EIDER.

REFERENCES CITED UNITED STATES PATENTS Name Date Pittlick Aug. 27, 1935 Number 

